Process for case-hardening iron and steel articles.



C. BURIAN. roonss ron CASH EARDENING IRON AND STEEL ARTICLES.

APPLIOATIOR PILED JULY 14, 1913.

1991286 Patented Mar. 24, 1914 E I War2wy V useful Improvements in an CARL BURIAN, OF BERLIN, GERMANY, AssIGNoR. 'ro THE rmM' OF GEBRDEB.

SCHUBERT, OFsBERIIN, GER/MANI'. I

'oonss FOR CASE-HARDENING IRON AND STEL ARTICLES.

Speciflcatin of Letters Patent.

- Patented Mar. 241914 Application filed .Tiny 14, 1913. Serial No. ?79,013,

To all whom it may concem Be it known that I, CARL BURIAN, citizen of the Empire of Germany, lin, Germany, have invented certain new and Improved Procf ess for Case-Hardening Iron and Steel Articles, of which the following is a specification.

y invention relates to an improved process for case-hardening iron and steel articles.

It has already been proposed to harden articles of low-carbon steel by coatin them with an adhesive mass containing a uid or pasty hardening composition and exposing them to the fire in 'that condition. It has also been proposed to add to the coating mass, saltpeter, common salt, glass and the like, which also serve as a bnding medium for the hardening agent' and are intended to prevent portions of same from dropping off into the fire. It has, however, been found in practice that satisfactory hardening cannot always be obtained by the aid of the means hitherto proposecl, since the binding media used crumble away-especially in an open fireand drop away, along with the hardening agent, from the surface of the articles to 'be hardened. According to my present inventio-n, this drawback is intended to be remedied by coating the article with a fluid or pasty hardening composition in the usualjway and then surrounding it with a band composed of highly refractory material and eoated with a hardening composition on both sides, the article so prepared being then eoated with a heat-rsisting mass or paste containing powdered fireresisting materials, such, for example, as asbestos, mica or the like. By means of the band, the hardening composition is reliabl retained against the surface to be hardened, no matter whether the hardening is performed in an open fire, in molten salts, a mutile, or in a metal bath.

Referring to the accompanying drawing, which illustrates a practical application of the process, the bolt 1 of iron is Wra ped twice at the part 2 to be hardened, wth a band 3. This wrapping carries on both sides the hardenin powder 4, which has been attached by a bin er The numeral 5 designates the loam, clay or like material which covers the bolt and its wrapping.

The following particulars may serve to residing at Ber-' illustrate the carrying out of my rocess by way of example: The portions of the work that are to be hardened are brushed over wth the sticky hardening composition, and the aforesaid band is lap Jed around the places which have been mad the band fits firmly dening powder has been applied' on both sides. The bands'can be made of any desred shape and size and of any desired width and thickness, as the particular conditions of the articles to be hardened regure. The article surrounded by the band in the manner described above, is then dipped in a liquid heat resisting mass or paste, to which finly powdered fireproof materials, such as asb like have been added; eoated over with such a paste or with loam and is then'allowed to dry thoroughly. The articles treated in this manner are warmcd up, n' any way, then heated to the hardening temperature, for example in a' molten salt When the case-hardenin is completed, the articles are freed from teir envelop by heating, and are cooled, as usual, in water or oil according to the character desired for them.

I claim 1. A process for case-hardening iron and or else the article is steel articles consisting in coating the articles on the places to be hardened with a hardening agent, in surrounding the eoated articles by a band containing a hardenng.

agent, in treating the articles so prepared 'With a heat 'esisting paste and in heating y `then to the hardening ten'perature.

2. A process for case-hardening iron and steel articles consisting in coating the articles on the places to be hardcned with a pasty hardening composition, in surroundin the eoated articles by a hand containing a ardening agent, in treating the articles so prepared with a heat resisting paste and in heating them to the harden-iug tcnpc': ture.

3. A process for case hardcuing iron and steel articles consisting in coating the ar( icles 'n the places to be hardcned with a hardening agent. in surrounding the roated articlesby a band of a highly rcfractoy inaterial containing a hardcning agcnl, in treatestos, mica and theto about 400 C., and are ing the articles so prepared with a heat resistng paste and in heating them to the cles on the places to be hardcned with a hardening agent, in surrounding the coated articles by a band containing a hardening agent, in treating the articles so prepared With loam and in heating them to the hardening temperature.

In testimony Whereof I have hereunto set my hand in`presence of two subscribing witnesses.

CARL BURIAN.

Witnesses WOLDEMAR HAUPT,

HENRY HASPER. 

